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Uruguayan Primrose - Ludwigia uruguayensis
Family: Onagraceae

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Description

Uruguayan water primrose is a herbaceous perennial and has two different growth forms: in one form glabrous or sparsely pubescent stems grow horizontally over the soil or water and produce roots at nodes and, often, white, spongy roots. These roots are feathery but stiff. Leaves are mostly glabrous, alternate, petiolate, but so congested at the tip to appear to be in rosettes. Leaf shape varies from suborbicular to obovate to spatulate with a round apex and base. Plants do not flower when only floating leaves are present.

In the other growth form, plants elongate from the rosette stage (described above) and grow above the surface of the water. The stems are pubescent and erect, up to 1 m tall. The leaves are pubescent, variable in shape from lanceolate to elliptic and acute at both ends. Upper leaves may be subsessile or sessile, the lower leaves petiolate. Flowers are solitary from the upper leaf axils and on stalks 2 to 3 cm long. Sepals and petals are 5, sometimes 6, the petals bright yellow. The fruit is a pubescent capsule with many seeds.

In general appearance and growth form, L. uruguayensis is similar to L. peploides (Kunth) Raven. The erect flowering stems, and long, shaggy hairs along the stem and on the leaves of L. uruguayensis are characters that can be used to separate it from L. peploides which typically is glabrous to sparsely pubescent and has flowering stems that are weakly ascending.

Interesting facts

Ludwigia uruguayensis is found in marshes, along marshy shores, in swamps, ponds and lakes, sloughs, ditches, irrigation and drainage canals. The horizontal stems may extend several meters from the shoreline into shallow water areas and form large floating mats. After senescence in the fall months, small leaves are produced along the stem and remain until regrowth begins in late winter or early spring (Aulbach-Smith & de Kozlowski 1996). Seeds may aid in species dispersion. Large colonies can prevent small boat navigation and recreational use of shoreline areas.

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Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers


Uruguayan Primrose Video


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